^^^ Cool! I guess my question really comes down to whether having one sub located in a corner loading position and one located mid-wall will do more to even the FR than say having two located either mid-wall on different walls or two corner loaded in different corners. It seems to me that having one in each location would go further in eliminating room nodes than two similarly positioned.

^^^ Cool! I guess my question really comes down to whether having one sub located in a corner loading position and one located mid-wall will do more to even the FR than say having two located either mid-wall on different walls or two corner loaded in different corners. It seems to me that having one in each location would go further in eliminating room nodes than two similarly positioned.

It always depends on the rooms, so it's good to experiment, but the principle in the multisubs paper is that opposite positions cancel out room modes. Different positions will stimulate different room modes, not cancel. In my room, opposite turned out to be a huge benefit.

Mid-wall vs. corner loading is a separate issue.

2 mid-wall has the benefits of stimulating fewer room modes for flatter frequency response and the symmetry on both major axes gives better seat-to-seat consistency.

Opposite corners is much more efficient and still benefits from cancelling some room modes on both major axes. You do sacrifice some seat-to-seat consistency.

4 subs in corners vs. 4 mid-wall subs is similar, except that both arrangements provide good seat-to-seat consistency, so it is just a question of efficiency vs. flat frequency response.

In my large room, with 2 subs, the mid-wall positions worked much better before EQ, but the opposite corner positions worked much better after EQ. Since I had no major null problems with the corner placement, I was able to cure the frequency response deficiencies with EQ, and the efficiency benefits were huge.

I ended up going with 4 subs in corners, which, when combined with good EQ, I would argue is the optimal choice for a closed rectangular room. In my room, the results with 1 sub were terrible. Going to 2 subs in opposite corners was a huge improvement. Going for 2 to 4 in each corner was a smaller improvement.

I showed my wife pictures of some of the setups on this board and explained to her, "See, I'm not crazy. THOSE guys are crazy. I'm being perfectly reasonable!"

From you recent reading Don, did you come across any information about the very center of a room? IIRC, isn't that the worst location for both subs and listeners?

Don't need to read about that, the center will always have a null! Comes straight from the math... Mine is around 30 Hz. The usual rule of thumb is to shoot for 1/3 or 2/3 of the way along the longest wall. I can't quite do that, but I had the couch moved off-center enough to get out of the null (mostly). I need to move my console forward a little for access so will be in that @#^%$ null again. I have a lot of treatment to help with modes, but am thinking of eliminating some and adding a couple of rear subs.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

For those of you with multiple subs, how much advantage was there in going from two to four? My room has serious modes and I set it up to move the listening position out of the major doublet, but need to re-arrange a bit and that will put the couch back in the mode. I have been reading Toole and various threads, plus running some calculations, and am thinking of picking up another pair of F12's. Part of my problem is they will have to go into the rear corners, and my front pair are not in but near the front corners, so I won't have optimal placement. Still, who can resist more subs?

As for how the subs will do in the rear corners, you can just place them there and measure their response and judge accordingly. Theoretical optimal placement can work but it may not necessarily be optimal for your room.

Thanks for the link. When I went to save the PDF, I discovered I already had it... Obviously the reminder was a good idea, thanks!

Yes, I will measure. I was more curious about the audible impact people had from going to multiple subs. I have seen skimmed a few more threads and done a little more off-line so it seems a Good Thing, confirming what I thought I already knew (too many decades since my grad acoustics courses, and HT was not around back then anyway -- but room modes were!) About the only way to mitigate a null (other than move out of it) is to put a source (sub) in it, and/or go to some sort of asymmetric (or at least quasi-asymmetric) placement to try to excite the modes differently in the room relative to the listening position. My room has two dimensions very close, a double null, blah.

If I don't move my main subs, I can use the sub output from my AVR (unused now) to drive the rear pair and save myself a little (phase) calibration effort.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

So, I'm working on a decent 2 channel budget system and I'm completely obsessed. Everything that I have I love and couldn't imagine doing a better job with my choices with the budget that was in front of me: Oppo 103, Peachtree NovaPre/220 combo and a sweet pair of Salk Songtowers.

The problem is not my equipment, it's my room. Last night I moved it all into a normal-ish 8ft ceiling, smaller room and it was COMPLETELY different. So rich, so deep, so clear and everything I hoped it would all be. I Moved it back to the living room/kitchen and I lost 60% at least. It's an acoustic nightmare. I have to be careful about room treatments as they will not fly with my fiance. No way. So, I need to fill in what is missing and that is bass. In the other room I could FEEL the music, in this room it's thin and sometimes fatiguing. I have to turn it up to levels too high to achieve the depth I'm looking for. So, I believe, the answer is a Rhythmic sub. Even if I could go all out with treatments, I think I would still need it in this room.

I traded a couple of emails with the good folks at Rhythmic and they suggested two F12's, or F15's. Sure that would be awesome, but like room treatments, I have to be careful. Not just with the money, but the aesthetics. I'm thinking one F12 and then add one in the Spring. This leads me to my questions:

1. My system will be used for 90% music. Jazz (been loving trios these days), funk, folk, jam and an occasional electronica (Pretty Lights, Bassnectar kind of stuff). The music is ALWAYS on. Will the F12 suffice, or should I go for the 15? Keep in mind, my goal will be two, so maybe two 15's wold be too much.

2. The NovaPre has a L and R pre out with no bass management. I'm thinking I would keep the Salks full range and just supplement the bass with the sub(s). Am I thinking correctly? So, I gather I get both a cable for the left and right both. Help me if I'm wrong.

3. From the picture below (sorry, the place is a mess), would you place the sub in that right corner, or should I move it between the speaker and the cabinet? I realize there will be some experimenting, but this is keeping me up at night and I'm dying to get some idea before I pull the trigger.

I had the setup where the green chair is and moved it to it's current position. It helped the SQ slightly and having everything in front of the window was useful. Had more sonic problems than I do now and it looked terrible. Over the next few months, I'll invest in some bass traps, but I'm not sure how much good they will do. Any insight on that would be greatly appreciated. I'll need more room treatments, but I need to do this gradually and slip them in from time to time without fanfare from the fiance ;)

I'm getting married in 13 days and would like to get a sub set-up before then. In two weeks I'll be forced to prioritize my finances somewhat and it will be harder to do. She agrees that the room sucks and it sounded killer in the spare room, but she doesn't care quite as much.

Sorry for the long-winded post, but I realize I'm with the nuts who think about this stuff all the time.

Thanks for the link. When I went to save the PDF, I discovered I already had it... Obviously the reminder was a good idea, thanks!

Yes, I will measure. I was more curious about the audible impact people had from going to multiple subs. I have seen skimmed a few more threads and done a little more off-line so it seems a Good Thing, confirming what I thought I already knew (too many decades since my grad acoustics courses, and HT was not around back then anyway -- but room modes were!) About the only way to mitigate a null (other than move out of it) is to put a source (sub) in it, and/or go to some sort of asymmetric (or at least quasi-asymmetric) placement to try to excite the modes differently in the room relative to the listening position. My room has two dimensions very close, a double null, blah.

If I don't move my main subs, I can use the sub output from my AVR (unused now) to drive the rear pair and save myself a little (phase) calibration effort.

It is a great paper to use as a rule of thumb. It sounds like you have an irregularly sized room or is your ceiling and one of the dimensions the same?

So, I'm working on a decent 2 channel budget system and I'm completely obsessed. Everything that I have I love and couldn't imagine doing a better job with my choices with the budget that was in front of me: Oppo 103, Peachtree NovaPre/220 combo and a sweet pair of Salk Songtowers.

The problem is not my equipment, it's my room. Last night I moved it all into a normal-ish 8ft ceiling, smaller room and it was COMPLETELY different. So rich, so deep, so clear and everything I hoped it would all be. I Moved it back to the living room/kitchen and I lost 60% at least. It's an acoustic nightmare. I have to be careful about room treatments as they will not fly with my fiance. No way. So, I need to fill in what is missing and that is bass. In the other room I could FEEL the music, in this room it's thin and sometimes fatiguing. I have to turn it up to levels too high to achieve the depth I'm looking for. So, I believe, the answer is a Rhythmic sub. Even if I could go all out with treatments, I think I would still need it in this room.

I traded a couple of emails with the good folks at Rhythmic and they suggested two F12's, or F15's. Sure that would be awesome, but like room treatments, I have to be careful. Not just with the money, but the aesthetics. I'm thinking one F12 and then add one in the Spring. This leads me to my questions:

1. My system will be used for 90% music. Jazz (been loving trios these days), funk, folk, jam and an occasional electronica (Pretty Lights, Bassnectar kind of stuff). The music is ALWAYS on. Will the F12 suffice, or should I go for the 15? Keep in mind, my goal will be two, so maybe two 15's wold be too much.

2. The NovaPre has a L and R pre out with no bass management. I'm thinking I would keep the Salks full range and just supplement the bass with the sub(s). Am I thinking correctly? So, I gather I get both a cable for the left and right both. Help me if I'm wrong.

3. From the picture below (sorry, the place is a mess), would you place the sub in that right corner, or should I move it between the speaker and the cabinet? I realize there will be some experimenting, but this is keeping me up at night and I'm dying to get some idea before I pull the trigger.

I had the setup where the green chair is and moved it to it's current position. It helped the SQ slightly and having everything in front of the window was useful. Had more sonic problems than I do now and it looked terrible. Over the next few months, I'll invest in some bass traps, but I'm not sure how much good they will do. Any insight on that would be greatly appreciated. I'll need more room treatments, but I need to do this gradually and slip them in from time to time without fanfare from the fiance

I'm getting married in 13 days and would like to get a sub set-up before then. In two weeks I'll be forced to prioritize my finances somewhat and it will be harder to do. She agrees that the room sucks and it sounded killer in the spare room, but she doesn't care quite as much.

Sorry for the long-winded post, but I realize I'm with the nuts who think about this stuff all the time.

Thanks so much in advance!

Rob

1. Looks like a pretty open layout; it is open to the rest of the place? If so I would definitely get the F15.
2. You'll need a summer, a resistive device that combines L/R but does not short them. Not just a Y cable... You can try with the Salks full-range and see if that works OK. In the long run you might consider rolling them off and letting the sub do its thing.
3. I can't really tell but it looks like the sub would be a little big either way. I'd probably go for the right corner, which will also give it a little more output (room gain).

HTH, IME, etc. - Don

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

I took at pic from the kitchen, so the behind me there's about two feet. So, it is open, but not huge. The rest of the house is two bedrooms, two baths. The house it tiny, but that area is awkward acoustically. It's that ceiling i think. It's gotta be closed 18ft at the peak.

I've been getting mixed messages as far as placement, but that will have to be resolved through experimentation. There really aren't too many options, so it will most likely end up in the corner.

So, I'm working on a decent 2 channel budget system and I'm completely obsessed. Everything that I have I love and couldn't imagine doing a better job with my choices with the budget that was in front of me: Oppo 103, Peachtree NovaPre/220 combo and a sweet pair of Salk Songtowers.

The problem is not my equipment, it's my room. Last night I moved it all into a normal-ish 8ft ceiling, smaller room and it was COMPLETELY different. So rich, so deep, so clear and everything I hoped it would all be. I Moved it back to the living room/kitchen and I lost 60% at least. It's an acoustic nightmare. I have to be careful about room treatments as they will not fly with my fiance. No way. So, I need to fill in what is missing and that is bass. In the other room I could FEEL the music, in this room it's thin and sometimes fatiguing. I have to turn it up to levels too high to achieve the depth I'm looking for. So, I believe, the answer is a Rhythmic sub. Even if I could go all out with treatments, I think I would still need it in this room.

Did you check polarity of the speaker wires ?

I traded a couple of emails with the good folks at Rhythmic and they suggested two F12's, or F15's. Sure that would be awesome, but like room treatments, I have to be careful. Not just with the money, but the aesthetics. I'm thinking one F12 and then add one in the Spring. This leads me to my questions:

1. My system will be used for 90% music. Jazz (been loving trios these days), funk, folk, jam and an occasional electronica (Pretty Lights, Bassnectar kind of stuff). The music is ALWAYS on. Will the F12 suffice, or should I go for the 15? Keep in mind, my goal will be two, so maybe two 15's wold be too much.

I have the F15 and for 2 channel its a LOT of subwoofer. If your eventually planning for 2, I would get two F12 and use it as Left and Right subwoofer, if space permits ..

2. The NovaPre has a L and R pre out with no bass management. I'm thinking I would keep the Salks full range and just supplement the bass with the sub(s). Am I thinking correctly? So, I gather I get both a cable for the left and right both. Help me if I'm wrong.

For 2 channel music, no filter required for the Salks. for HT I would used the HPF Filter on the subwoofer . You can do this, since you have pre- and power in on your amp.

3. From the picture below (sorry, the place is a mess), would you place the sub in that right corner, or should I move it between the speaker and the cabinet? I realize there will be some experimenting, but this is keeping me up at night and I'm dying to get some idea before I pull the trigger.

I had the setup where the green chair is and moved it to it's current position. It helped the SQ slightly and having everything in front of the window was useful. Had more sonic problems than I do now and it looked terrible. Over the next few months, I'll invest in some bass traps, but I'm not sure how much good they will do. Any insight on that would be greatly appreciated. I'll need more room treatments, but I need to do this gradually and slip them in from time to time without fanfare from the fiance

I'm getting married in 13 days and would like to get a sub set-up before then. In two weeks I'll be forced to prioritize my finances somewhat and it will be harder to do. She agrees that the room sucks and it sounded killer in the spare room, but she doesn't care quite as much.

Sorry for the long-winded post, but I realize I'm with the nuts who think about this stuff all the time.

IF you're looking to minimize/eliminate room modes, then placing your subs in modal nulls is the easiest way to do that. Here's an explanation from Toole:

From a frequency response perspective the 1/4, 3/4 position is best. Technically, doing that on both axes with the subs out in the room would be ideal for FR.
From an efficiency perspective, corner loading is ideal, and putting the subs out in the room would be terrible.

Good point. I guess room treatment is more effective up there, but I guess all frequencies above the XO would have a dip, depending on your speaker placement.

Getting enough room treatments to treat bass frequencies adequately is still difficult, thus it's preferable to locate the LP and subs properly. I know I don't want to fill my room with even MORE stuff . Treating the rear wall with bass absorbers/diffusors would definitely help attenuate the bass bouncing off the back wall.

Sure, a regular room might have dips in the bass region but being in the center of the room still makes it much worse.

Don't need to read about that, the center will always have a null! Comes straight from the math...

Q: Which mode gives you a center null with subs on opposite sides?
A: None.

Hilarious. Genius. Obviously I should have been more explicit that I was speaking of the room itself, not how it changes when you add sources. And it depends upon getting the subs' phasing correct, of course.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

Ceiling is about 1/2 the length. Plus it is a little irregular so the simple modal formula doesn't quite apply, and I haven't felt like trying COMSOL or the like.

I've only ever used MATLAB

I have Matlab and Mathcad. I had a prototype copy of COMSOL but have not used it for several years, one of those things that looked really worthwhile but unfortunately not enough time to play... I don't have the flow analysis toolkit (not sure if they have one but more than likely they do) and haven't tried to do more than basic modal calculations with Matlab or Mathcad. There were some nifty audio analysis programs on the Matlab user's site at one time (have not looked for a while). I had a flow analysis package for Mathcad but have not updated my copy for ages. And somehow don't seem to have increased my quantity of free time...

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

I finally decided to add a Rythmik sub to establish a foundation to my Magnepan MG3a's with DWM woofer panels. I got the E15HP. Gorgeous finish!

I placed it exactly where past experiments with subs worked best (38% out in the room along the side wall with woofer cones exactly equidistant to me as my main speakers). The sound was immediately vastly superior to any previous sub in the room. The bass was tighter, pitch definition was much better and mid range clarity was substantially improved. These are definitely fantastic subs for integrating with Maggies.

With one day of experimentation, it was easy to get flat frequency response (a Radio Shack SPL Meter is the best purchase ever in audio). However, this is probably because I have played around with subs before, and my main system was flat down to 32 hz to start with (adding DWM panels to three series Maggies is highly recommended.) All I really had to do was fill in the very bottom end.

Here are my settings:
Limiter off.
PEQ off
Delay phase 0 degrees
Crossover 32
Volume almost three quarters
Low pass 50/24
Rumble off
14hz high Damping
I use it solely for two channel stereo music with no AVR.

Again, the sound already blows away the sound of the speakers without a sub or the sound with a prior Mirage sub. My question to the forum is how do I tweek out the last bit of improvement from the settings?

I plan on playing around more with the phase. Do I just get someone to dial it and listen for optimal bass (my preliminary tests point to zero to twenty as optimal)? Or is there a technical algorithm? Is there a formula for dialing it in based upon relative difference in distance to listening seat from main woofers? Or do I set it for optimal bass output at the crossover frequency and then adjust everything from there? If so, what frequency do I optimize around? 50 which is the setting on my switch, 32, which is the setting on the crossover knob, or 25 which is my minus 3db point on the mains?

Any help on the phase procedure would be massively appreciated.

We have a Java scripts helping customers to do the integration (in case customers do not have bass management) : www.rythmikaudio.com/subtuner2.html. The script gives you recommended crossover and phase adjustment based on your driver diameter in your front speakers and whether it is sealed for vented (transmission line is treated same as vented sub). When the script was written, it didn't consider planar speakers, but it is not hard to work around it. Sealed front speakers have 2nd order roll-off, vented front speakers have 4th order roll-off and planar front speakers have 3 order roll-off. So you can try sealed front speaker configuration sealed front speakers first (use 10 diameter) and try vented from speakers. The phase adjustment you need should be somewhere between these two recommended settings. In actual listening test, you can start with the recommended setting and gradually change 1 clock position up or down at a time. When you get the correct alignment, the energy around the crossover point should sound more firmed up.

Quote:

This gets me to the second question. What exactly does the crossover knob do? When I set the 50/24 switch am I NOT getting 24 db roll off at 50hz? Am I really getting 12 db per? By setting the crossover knob at 32 is it starting to roll off earlier? Steeper? Both?

If you set the crossover knob also at 50hz, then you can true 50hz/24db roll-off. If you move the knob to 32hz, then between 32hz and 50hz and it is still technically 12db. The customers shouldn't be too concerned about the exact corner frequency. Phase alignment is what we need to be concerned with.

True, but the null can be addressed with a couple of placement options: you can either place a subwoofer in the null itself at the centre of the room OR place a pair of subs equal distances apart from the centre of the room.

The former placement works because a room mode cannot be excited when the source of pressure (sub) is in its null. The latter placement works because modes have polarity, so placing a pair of subs on opposite sides of the null will excite the mode positively and negatively, cancelling at the null location.

Think of the mode as a swing in a playground. The first method is like keeping any of the kids from touching the swing. The swing doesn't move (mode isn't excited). The second method is like having two kids push equally hard on opposite sides of the swing. The swing doesn't move (mode isn't excited).

Both methods can be combined, as shown in the Toole paper in my previous post. Placing a pair of subs at the 1/4 and 3/4 locations of room width will put them in the nulls of the 2nd width mode, thereby minimizing those nulls. And, since they are equidistant from the centre of the room, they will also minimize the 1st and 3rd width modes.

Careful read of my follow-up posts will reveal that I know that and have read Toole (among others); I was addressing a question about the room itself. Been decades since my grad acoustics courses and all those years doing installs and such but I remember a tiny bit of wave theory...

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley

^^^ Cool! I guess my question really comes down to whether having one sub located in a corner loading position and one located mid-wall will do more to even the FR than say having two located either mid-wall on different walls or two corner loaded in different corners. It seems to me that having one in each location would go further in eliminating room nodes than two similarly positioned.

I think it was you who has a similar room to mine (could be equipment). My room is 18x13.5x75 feet roughly... I have a bad peak near the same frequency as yours with the sub in the corner. Try the midpoint of the nearest wall to your seat, about 3" off the wall. It works well for me either with the driver facing me or facing to parallel to the wall but I face it parallel to stick out from the wall less. Give it a shot, it takes the sub from a one-note boom to a nice response. And one FV15HP has way more output than required in a room that size.

^^ Output is not the main reason for multiple subs. Smoother FR is another main reason. My room is slightly bigger than yours (14x19x9.5') and thought a single fv15 is all I needed but thanks to this forum that convinced me to spend more money (as usual), I went with dual fv15hps and the difference is significant (proven by REW graph). I played some heavy bass clips and turned off one sub and I was like 'what the heck happening?. Turn it back on, and wow that is how bass supposed to be. Can't go back with one sub any more. This is the biggest upgrade/addition to my system. I tried external amps (Bryston 5 channels) and some expensive pre-amp ($6000 Lexicon mc1) more than a decade ago and for movie, I could not hear a difference. Adding a second sub, I immediately can hear a huge difference.

^^ Output is not the main reason for multiple subs. Smoother FR is another main reason. My room is slightly bigger than yours (14x19x9.5') and thought a single fv15 is all I needed but thanks to this forum that convinced me to spend more money (as usual), I went with dual fv15hps and the difference is significant (proven by REW graph). I played some heavy bass clips and turned off one sub and I was like 'what the heck happening?. Turn it back on, and wow that is how bass supposed to be. Can't go back with one sub any more. This is the biggest upgrade/addition to my system. I tried external amps (Bryston 5 channels) and some expensive pre-amp ($6000 Lexicon mc1) more than a decade ago and for movie, I could not hear a difference. Adding a second sub, I immediately can hear a huge difference.

Yes my point was the placement of the sub and seating making a hige difference in sound quality, the output was a sideline. I'm far fussier than anyone else that watches movies here, so positioning best for the primary listening seat is acceptable as long as the others aren't too far off. And the positioning I have now is pretty even, good enough for me to not want to spend big bucks to improve. Corner placement of the sub was unacceptable and my reason for posting is that I think torqdog's room dimensions are similar to mine, so he should try the sub out of the corner.

I think it was you who has a similar room to mine (could be equipment). My room is 18x13.5x75 feet roughly... I have a bad peak near the same frequency as yours with the sub in the corner. Try the midpoint of the nearest wall to your seat, about 3" off the wall. It works well for me either with the driver facing me or facing to parallel to the wall but I face it parallel to stick out from the wall less. Give it a shot, it takes the sub from a one-note boom to a nice response. And one FV15HP has way more output than required in a room that size.

Nope, it's definitely not the room but we did converse a while back regarding our PSB Golds and Oppo 95. My room is the dreaded square (24 x 24 x 10) and I've got things positioned about as good as I can, given what I have to work with. I actually found the best position for my FV15HP was approx 3 1/2 feet out from the front and side wall in the corner with the driver facing the corner.

BTW; last time we talked I was looking for a C-6i center. I never did find one and instead found another Gold that I am using as my center with excellent results.